This invention relates to a light-sensitive silver halide color photographic material having high sensitivity as well as excellent image quality, more particularly to a light-sensitive silver halide color photographic material which is high in sensitivity and can also exhibit excellent sharpness and graininess.
Heretofore, for light-sensitive silver halide color photographic material (hereinafter abbreviated as light-sensitive material), development of a light-sensitive material having high sensitivity and excellent image quality has been desired. Particularly, in recent years, with the increase of photographing under bad conditions with small quantity of light and small formatting of a light-sensitive material, development of a light-sensitive material excellent in sharpness and graininess has been strongly desired. However, it has been difficult to improve image quality along with higher sensitization.
For example, as the technique for higher sensitization, the technique has been known in which a layer constitution of regular sequence having respective layers of red-sensitive, green-sensitive and blue-sensitive light-sensitive silver halide emulsion layers (light-sensitive silver halide emulsion layer is hereinafter referred to merely as "emulsion layer") is provided by coating on a support, a part or whole of the light-sensitive emulsion layers being separated into a high sensitivity silver halide emulsion layer (hereinafter referred to as high sensitivity emulsion layer) and a low sensitivity silver halide emulsion layer (hereinafter referred to as low sensitivity emulsion layer), each containing a diffusion resistant coupler capable of color forming to substantially the same hue, and wherein these layers are laminated adjacent to each other. According to such a constitution, there is involved the problem that the emulsion layer on the side nearer to the support will suffer from absorption of light by other emulsion layers positioned on the side farther from the support during exposure. Moreover, during development, a considerably long time is required for diffusion of a developer. Thus, according to such a layer constitution of regular sequence, due to loss in dosage of exposure and retardation in development, it is difficult to achieve higher sensitization in green-sensitive and red-sensitive emulsion layers positioned as lower layers.
On the other hand, techniques to alter the order of respective emulsion layers laminated are known.
For example, U.S. Pat. No. 3,663,228 discloses a constitution comprising:
(a) the respective low sensitivity emulsion layers of red-sensitive, green-sensitive and blue-sensitive layers provided by coating on a support in the order mentioned from the support side; and
(b) the respective high sensitivity emulsion layers of red-sensitive, green-sensitive and blue-sensitive layers provided by coating on the side farther from the support in the order mentioned from the support side, as shown in FIG. 1C annexed to the specification. This technique can afford higher sensitivity as compared with the constitution of regular sequence as described above. However, as can clearly be seen from the fact that each unit of laminates of the aforesaid high sensitivity emulsion layer and low sensitivity emulsion layer are separated by ND (neutral density) filter, higher sensitization is not the gist of interest.
Next, U.S. Pat. No. 3,658,536 discloses a technique to cancel loss of dosage in a green-sensitive emulsion layer having great effect on visual sensitivity by positioning the green-sensitive emulsion layer on the surface side farther from the support, as shown in FIG. 5 annexed to the specification. However, according to such a layer constitution, high sensitization technique of a blue-sensitive emulsion layer is not dealt with at all, and also improvement of sharpness and graininess is not satisfactory.
Otherwise, there have also been known techniques concerning alteration of the layer constitution as disclosed in Japanese Provisional Patent Publications No. 49027/1976 and No. 97424/1978 and U.S. Pat. No. 4,129,446. However, any of these techniques, while higher in sensitivity than the layer constitution of regular sequence as described above, is not only unsatisfactory in sensitivity of green-sensitive and red-sensitive emulsion layers but also unsatisfactory in effects of improvement of image quality such as graininess and sharpness.
In the light of the state of the art as mentioned above, the present inventors have continued to study cancelling the drawbacks or inconveniences of the prior art and consequently already invented and proposed a technique as disclosed in Japanese Provisional Patent Publication No. 177551/1984. This technique provides a light-sensitive material comprising at least one layer of green-sensitive silver halide emulsion layer, at least one layer of red-sensitive silver halide emulsion layer and a plural number of blue-sensitive silver halide emulsion layers with different sensitivities provided on a support, wherein one of the said plural number of blue-sensitive silver halide emulsion layers is provided as the silver halide emulsion layer positioned on the side farthest from the support, said respective at least one layer of green-sensitive silver halide emulsion and at least one layer of red-sensitive silver halide emulsion are provided between the said blue-sensitive silver halide emulsion layer provided on the farthest side and a blue-sensitive silver halide emulsion layer lower in sensitivity than the said blue-sensitive silver halide emulsion layer, further at least one layer of silver halide emulsion layers of said green-sensitive layer and red-sensitive layer sandwiched between the said two blue-sensitive emulsion layers, including the said two blue-sensitive emulsion layers, contain mono-dispersed silver halide grains, and at least one layer of the green-sensitive emulsion layers sandwiched between the said two blue-sensitive emulsion layers contains a colored magenta coupler.
According to the technique of the prior technique by the present inventors, any of blue-sensitive, green-sensitive and red-sensitive emulsion layers can be made higher in sensitivity and at the same time excellent sharpness and graininess can be exhibited.
The present inventors have further continued to study such a technique according to the prior proposal and consequently completed a novel technique capable of exhibiting equal to or more excellent characteristics than said prior technique by way of a technique different from said prior technique to accomplish the present invention.
Accordingly, a first object of this invention is to provide a light-sensitive material in which any of blue-sensitive, green-sensitive and red-sensitive emulsion layers has high sensitivity.
A second object of this invention is to provide a light-sensitive material which is high in sensitivity and can also exhibit excellent sharpness and graininess.
A third object of this invention is to accomplish the above first and second objects by way of a technique different from that according to the prior technique by the present inventors.
A fourth object of this invention is to provide a light-sensitive material which can improve graininess better than the above technique of the prior technique, while maintaining sharpness.
Other objects will be apparent from the following description in this specification.